 /*******************************************************************************
  * Copyright (c) 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.commands.operations;

 import org.eclipse.core.runtime.IAdaptable;
 import org.eclipse.core.runtime.IStatus;

 /**
  * Extends {@link IOperationApprover} to approve the execution of a particular
  * operation within an operation history. Operations that are candidates for
  * execution have already been validated against their current state and
  * according to the rules of the history. Prior to 3.2, an operation approver
  * was only consulted for undo and redo of an operation, not its initial
  * execution.
  * <p>
  * By the time an IOperationApprover2 is consulted, the execution has already
  * been requested and it has been determined that the operation is valid.
  * Approvers should return an <code>IStatus</code> object with severity
  * <code>OK</code> if the operation should proceed, and any other severity if
  * it should not. When an operation is not approved, it is expected that the
  * object not allowing the operation has already consulted the user if necessary
  * or otherwise provided any necessary information to the user about the fact
  * that the operation is not approved.
  * </p>
  * <p>
  * Like {@link IOperationApprover}, implementers of this extension must be
  * prepared to receive the approval messages from a background thread. Any UI
  * access occurring inside the implementation must be properly synchronized
  * using the techniques specified by the client's widget library.
  * </p>
  *
  * @since 3.2
  */
 public interface IOperationApprover2 extends IOperationApprover {
     /**
      * Return a status indicating whether the specified operation should be
      * executed. Any status that does not have severity <code>IStatus.OK</code>
      * will not be approved. Implementers should not assume that the execution
      * will be performed when the status is <code>OK</code>, since other
      * operation approvers may veto the execution.
      *
      * @param operation
      * the operation to be executed
      * @param history
      * the history performing the execution of the operation
      * @param info
      * the IAdaptable (or <code>null</code>) provided by the
      * caller in order to supply UI information for prompting the
      * user if necessary. When this parameter is not
      * <code>null</code>, it should minimally contain an adapter
      * for the org.eclipse.swt.widgets.Shell.class. Even if UI
      * information is provided, the implementation of this method
      * must be prepared for being called from a background thread.
      * Any UI access must be properly synchronized using the
      * techniques specified by the client's widget library.
      * @return the IStatus describing whether the operation is approved. The
      * execution will not proceed if the status severity is not
      * <code>OK</code>, and the caller requesting the execution will
      * be returned the status that caused the rejection. Any other
      * status severities will not be interpreted by the history.
      */
     IStatus proceedExecuting(IUndoableOperation operation,
             IOperationHistory history, IAdaptable info);
 }
